An axis alignment detector for aligning axes of two birefringent components or fibers at forty-five degrees relative to each other. Polarized light is put into one axis of one of the two components or fibers to be aligned. The light goes from the one fiber through a junction where the two components or fibers are to be aligned at forty-five degrees, into the axes of the other component or fiber. The other component or fiber is temporarily connected to a third birefringent component or fiber wherein light moves on into the third component or fiber. The light from the third component or fiber goes on through a polarizer on to a mirror or integrated optic interferometer. The interferometer provides an interference output that reveals when the two components or fibers have a forty-five degree axis alignment. Also, the interferometer output may be used to measure other angles of axis alignment. One light path of the interferometer is modulated and the interferometer output is converted to an electrical signal which is electronically processed to improve detection of an accurate forty-five degree alignment of the to-be-joined or spliced pair of birefringent components or fibers.